Downloading app when connected to PC

[minx11]

I am new to Ipad so might be a basic question - I have an ipad 2 and having trouble downloading apps over 50mb. I get the message to use WiFi (which I dont have) or connect to computer. I connect it to PC but can't work out how to get it to download. I go to Itunes and look up the app (IMOvie) and it says its downloaded but when I go to my Ipad its asks me to install - then I get the same message again! Help!!!